Electrical switching arrangement with multiple interruption



3,448,287 ELECTRICAL SWITCHING ARRANGEMENT WITH MULTIPLE INTERRUPTION Salvatore Giammona, Sao Paulo, Brazil, assignor to Aktiengesellschaft Brown Boveri & Cie, Baden, Switzerland, a joint-stock company Filed Aug. 23, 1966, Ser. No. 574,454 Claims priority, application Switzerland, Sept. 29, 1965, 13,449/ 65 Int. Cl. H01h 9/40 US. Cl. 307136 1 Claim ABSTRACT OF THE DISCLOSURE An electrical power switching arrangement comprises a plurality of main power switching points connected electrically in series. Each main switching point formed by a pair of switch contacts is bridged by a series circuit arrangement of a resistor and an auxiliary switching point established also by a pair of auxiliary switch contacts. The operating sequence is such that when switching off, all of the main switching points disconnect simultaneously and all of the auxiliary switching points also disconnect simultaneously but with a delayed action so as to follow disconnection of the main switching points. When switching on, a first group of the main switching points close simultaneously, and all of the auxiliary switching points also close simultaneously and at the same time as the main switching points of the first group. The remaining main switching points then close simultaneously but with a delayed action after the first group.

The present invention relates to an electrical switching arrangement and more particularly to an improvement on a type of switch which provides so-called multiple interruption, i.e., a plurality of main, power switching points are connected electrically in series, and each main switching point, formed by a pair of relatively movable contact members, is paralleled, i.e., bridged by a series circuit arrangement of a resistor and an auxiliary switching point. When switching off, all of the main interrupting switching points disconnect simultaneously and all of the auxiliary switching points also disconnect simultaneously but with a delayed action in relation to the switching off of the main points of interruption.

The use of a resistor in parallel with each main, power switching point which is disconnected by the auxiliary switching point after the main switching point has opened serves the purpose of establishing a uniform voltage distribution for the various switching sections on the one hand, and they also beneficially influence the build-up voltage over the switch. In order to limit excessive voltages which can occur in certain switching situations during a contact making, i.e., during a switching-on operation, so-called circuit closer resistances have been provided in recent years for high voltage switches. These resistances can be provided separately from the resistors mentioned above used during a switching-01f operation, or one and the same resistance element can be used both for switching-off and for switching-on operations. The use of separate resistances, one for switching-off and another for switching-on results in the obvious disadvantage of materially increasing costs, this primarily because of the additional auxiliary switching points which are required.

Furthermore, the space requirements for separate resistances and their associated auxiliary switching points used to disconnect the resistances become considerable. On the other hand, the use of one and the same resistance element and auxiliary switching point for both switchingoff and switching-on operations is not without disadvan- United States Patent ice tage because of the difliculty in the electrical design of the resistance elements themselves. This is due to the fact that for a switching-on operation, the resistance should have an ohmic value which should 'be lower by a factor of two than that of the resistance used for a switching-oft operation. Moreover, the period of time that the resistance is under load during a switching-on operation is shorter than the load period during a switching-oft operation so that use of the same resistance element for both functions leads to an unfavorable resistancedesign because it has to be dimensioned, from a standpoint of its current load carrying ability for the less favorable function of switching-off.

The object of the present invention is to overcome this difiiculty and has for its principal aim to enable the switch to perform a switching-on operation, without the use of additional resistances and auxiliary switching points, with a resistance whose ohmic value is substantially lower than the value used during a switching-01f operation. This objective is attained by the use of a single set of resistances and auxiliary switching points but wherein the operating instants of the main switching points are so controlled that during a switching-on operation, only a first group of the total number of main switching points are closed simultaneously while the remaining main switching points are thereafter closed simultaneously but with a delayed action in relation to closure of the first group. All of the auxiliary switching points are closed simultaneously and at the same time as closure of the first group of main switching points takes place. When switching-off, all main switching points open simultaneously and all auxiliary switching points also open simultaneously but with a delayed action in relation to opening of the main switching points.

One suitable embodiment for the invention will be described hereinafter in detail and is illustrated in the accompanying drawing, the single figure of which is an electrical schematic of the various operating components of the improved power switching device.

With reference now to the drawing, the power switching device is seen to be comprised of a plurality of power switching points 1a to lg which are connected electrically in series to a line L to be controlled. Connected in parallel with each of these power switching points is a series arrangement of a resistance and an auxiliary switching point for connecting the resistance into and out of its parallel circuit arrangement with the power switching point. These resistances are designated by 2a2g and their respective auxiliary switching points by 3a-3g. Each of these auxiliary switching points has its own actuating mechanism or drive and these are designated by 4a-4g. A suitable construction for such a drive and illustrating the arrangement of the contacts 3a-3g and resistances 2a-2g is described in US. Patent No. 2,665,351, issued Jan. 5, 1954, in the name of Ha-akon Forwald.

One group of the power switching points 1a, 1b and 1c are actuated together by a common drive mechanism 5, and the remaining switching points 1d, 1e, 1f and 1g are likewise actuated together by a common drive mechanism 6. A suitable construction for such a drive and illustrating the arrangement of the contacts 1a to 10 and 1d to lg as well as the drives 5 and 6 is likewise illustrated in the aforesaid Patent No. 2,666,351.

For switching otf the power switching points and for switching off the auxiliary switching points an Off control apparatus 7 is employed and this is used to control the drive mechanisms 5 and 6 jointly so that the power switching points 1a1g open simultaneously. The Off control apparatus 7 is also used to control the drive mechanisms '4a4g jointly so that the latter open their respectively controlled auxiliary switching points 3a-3g simultaneously but a time delay unit '8 is interposed between the control 7 and drive mechanisms 4a-4g so that the auxiliary switching points 3a-3g open after the main power switching points la-lg have opened.

When a switching-on operation is desired, an 011 control 10 is utilized and this actuates drive methanism 6 for the power switching points 1d-1g directly, i.e., without any delay. The On control also actuates drive mechanism for the power switching points la-lc but a delay unit 9 is interposed between the On control and drive 5 so that the main power switching points la-lc close somewhat later than do the power switching points ld-lg. The On control is also used to actuate all ot the drives 4a-4g for the auxiliary switching points 3a-3g simultaneously to their closed positions and at the same time that the power switching points ld-lg are closed. A suitable construct-ion for the delay units 8 and 9 is described in Swiss Patent No. 343,484, published Feb. 15, 1960, and a suitable construction for the Control Off and Control On units 7 and 10- is described in British Patent No. 980,247, published Jan. 13, 1965.

The advantage derived from this improved arrangement is that by closing the power switching points in two stages, i.e., in two groups, one group being delayed, a portion of the switching-off resistances, namely 2a-2c become effective as switching-on resistances because the main switching points la-lc which close with the delay action, force a current path via the resistances 2a-2c and because the auxiliary switching points 3a-3g have already closed simultaneously with closure of the other group of main switching points ld-lg.

I claim:

1. In an electrical switching device the combination comprising a plurality of main power interrupt-ing points arranged in first and second groups and which are connected electrically in series, each of said groups including a plurality of series connected sets of main switching contacts, a resistance and an auxiliary interrupting point constituted by a set of auxiliary switching contacts arranged in a series circuit with said resistance and which circuit is connected in parallel with each of said sets of main switching contacts, first and second drive means for actuating simultaneously the sets of main switching contacts of said first and second groups, respectively, a third drive means for actuating simultaneously all of the sets of auxiliary switching contacts, a switching-off control means for actuating all of said drive means, said first and second drive means being actuated directly by said switching-off control means to effect immediate and simultaneous action of all of said sets of main switching contacts from closed to open position, and said third drive means being actuated indirectly by said switchingotf control means through a first delay unit thereby to elfect simultaneous but delayed actuation of all of said sets of auxiliary switching contacts from closed to open position, and a switching-on control means for also actuating all of said drive means, said first and third drive means being actuated directly by said switching-on control means to elfect immediate and simultaneous actuation of all of said sets of main switching contacts of said first group and all of said sets of auxiliary switching contacts from open to closed position, and said second drive means being actuated indirectly by said switching-on control means through a second delay unit thereby to effect simultaneous but delayed actuation of all of said sets of main switching contacts of said second group from open to closed position.

References Cited UNITED STATES PATENTS 3,114,816 12/1963 Beatty 20 0144 3,192,440 6/ 1965 Baltensperger 200144 3,284,648 11/ 1966 Koppelmann 30 7136 3,366,837 1/ 1968 Mester 317- 11 ROBERT K. SCHAEFER, Primary Examiner.

T. B. JOIKE, Assistant Examiner.

U.S. C1. XR. 

